Many pieces of lawn and garden, groundskeeping and agricultural equipment have rotating cutting blades for shearing vegetable matter. This class of equipment may be termed "rotary cutters." The simplest rotary cutter design is found in the common lawn mower, in which a double blade is affixed to a rotating central shaft. In many larger pieces of equipment, the blade is not directly connected to the rotating central shaft but instead to a horizontal crossbar which in turn is connected to the central shaft. One end of each of two or more blades is pivotally affixed to the crossbar, while an opposed end of each of these blades is permitted to swing free. In normal operation of the rotary cutter, the free end is thrown outward by "centrifugal" force. But when the blade encounters an obstacle that resists being displaced or sheared, such as a rock or other solid object, a free end of the blade will pivot back around the pin, and then resume a straight-out position through "centrifugal" force after the obstacle is cleared.
While such blades are designed to freely articulate in a plane orthogonal to the pin axis, such as a horizontal plane, it is undesirable for such blades to have more than a minimum of play in a direction parallel to the pin axis (e.g. the vertical direction). A swinging blade that has too much vertical play will begin to score the deck or cover of the cutter apparatus, dulling the blade and even perforating the deck plate.
As a result contacting nonvegetable matter, the blades and cutting devices invariably get damaged and become loose on the mechanical shaft or mechanism responsible for their rotation. Moreover, as a result of ordinary use, it is not uncommon for parts of rotary cutters to corrode and for their blades or cutting devices to become dull and require sharpening and cleaning.
When rotary cutters require replacement parts, cleaning, tightening or repair, the procedure for doing so is often complicated for the user. As will be explained below, one prior art technique for affixing a cutter blade to another member such a crossbar is to make bores in the cutter blade and the crossbar and to insert a pin in the bores. The pin may be fabricated with a circumferential groove against which a slot in a keyhole plate is slid home. The vertical play between the members is adjusted by the use of shims or spacers between one surface of the crossbar and the keyhole plate; these spacers vary in number and thickness. A blade pin lock clip is bolted onto the crossbar and against the circumferential groove of the pin to hold the entire assembly together. In time, corrosion of the parts will make them difficult to remove.
It is difficult to perform a field adjustment of the right amount of vertical play between the pivoting member and the other member by selecting among a set of spacers, which spacers must be provided and carried separately.
In other prior art designs, a threaded pin is inserted into bores in the blade and blade carrier or crossbar and retained with a hex nut. After some use the blade pin and hex nut corrode, making disassembly very difficult.
A need therefore exists to develop a pivoting blade attachment mechanism that makes installing, adjusting, repairing and cleaning easier for users of rotary cutters of various types.